Mask orientation

ABSTRACT

A method of forming patterned features on a substrate is provided. The method includes positioning a plurality of masks arranged in a mask layout over a substrate. The substrate is positioned in a first plane and the plurality of masks are positioned in a second plane, the plurality of masks in the mask layout have edges that each extend parallel to the first plane and parallel or perpendicular to an alignment feature on the substrate, the substrate includes a plurality of areas configured to be patterned by energy directed through the masks arranged in the mask layout. The method further includes directing energy towards the plurality of areas through the plurality of masks arranged in the mask layout over the substrate to form a plurality of patterned features in each of the plurality of areas.

CROSS-REFERENCE TO RELATED APPLICATION(S)

This application is a continuation application of co-pending U.S. Pat.Application Serial No. 17/571,039, filed Jan. 7, 2022, which is acontinuation of U.S. Pat. Application Serial No. 16/735,603 filed Jan.6, 2020, the entire contents of which are each hereby incorporatedherein by reference.

BACKGROUND Field

Embodiments of the present disclosure generally relate to methods offorming patterns in substrates, for example using masks to transferpatterns to substrates.

Description of the Related Art

Transferring patterns to substrates, such as semiconductor substrates,is often accomplished using masks. For example, photolithography can beused to transfer patterns in the masks to a photoresist disposed on thesubstrate. Because the patterns to be formed on the substrate correspondto the patterns on the mask, the complexity of the patterns to be formedon the substrate directly effect the complexity and thus costs offorming the corresponding masks. Furthermore, increases in thecomplexity of a mask (e.g., number of features) can cause reductions inthroughput when a substrate is being processed with a more complex maskcompared to a process being processed with a less complex mask.

Therefore, there is a need for methods and corresponding equipment whichcan reduce mask complexity and increase throughput for substrateprocessing.

SUMMARY

Embodiments of the present disclosure generally relate to methods offorming patterns in substrates, for example using masks to transferpatterns to substrates. In one embodiment, a method of forming patternedfeatures on a substrate is provided. The method includes positioning aplurality of masks arranged in a mask layout over a substrate, whereinthe substrate is positioned in a first plane and the plurality of masksare positioned in a second plane, the plurality of masks in the masklayout have edges that each extend parallel to the first plane andparallel or perpendicular to an alignment feature on the substrate, thesubstrate includes a plurality of areas configured to be patterned byenergy directed through the masks arranged in the mask layout, theplurality of areas configured to be patterned are spaced apart from eachother by one or more areas not configured to be patterned by the energydirected through the masks, and each area of the plurality of areasconfigured to be patterned is spaced apart from a closest area of theplurality of areas configured to be patterned by a shortest distancealong a direction offset by at least 5 degrees from directions in thefirst plane that extend parallel or perpendicular to the alignmentfeature on the substrate. The method further includes directing energytowards the plurality of areas through the plurality of masks arrangedin the mask layout over the substrate to form a plurality of patternedfeatures in each of the plurality of areas, wherein a number of theformed plurality of patterned features extending along directions in thefirst plane that are within ±2.5 degrees of being parallel orperpendicular to the alignment feature are greater than a number of theformed plurality of patterned features extending along directions in thefirst plane that do not align within ±2.5 degrees of being parallel orperpendicular to the alignment feature.

In another embodiment, a method of forming patterned features on asubstrate is provided. The method includes positioning a plurality ofmasks arranged in a mask layout over a substrate that is positioned,wherein the substrate is positioned in a first plane and the pluralityof masks are positioned in a second plane, the plurality of masks in themask layout have edges that each extend parallel to the first plane andparallel or perpendicular to an alignment feature on the substrate, thesubstrate includes a plurality of areas configured to be patterned byenergy directed through the masks arranged in the mask layout, theplurality of areas configured to be patterned are spaced apart from eachother by one or more areas not configured to be patterned by the energydirected through the masks, and each area of the plurality of areasconfigured to be patterned is spaced apart from a closest area of theplurality of areas configured to be patterned by a shortest distancealong a direction offset by at least 5 degrees from directions in thefirst plane that extend parallel, perpendicular, ±30 degrees, ±45degrees, or ±60 degrees relative to the alignment feature on thesubstrate. The method further includes directing energy towards theplurality of areas through the plurality of masks arranged in the masklayout over the substrate to form a plurality of patterned features ineach of the plurality of areas, wherein a number of the formed pluralityof patterned features extending along directions in the first plane thatare within ±2.5 degrees of being parallel, perpendicular, ±30 degrees,±45 degrees, or ±60 degrees relative to the alignment feature aregreater than a number of the formed plurality of patterned featuresextending along directions in the first plane that do not align within±2.5 degrees of being parallel, perpendicular, ±30 degrees, ±45 degrees,or ±60 degrees relative to the alignment feature.

In another embodiment, a method of forming gratings on a substrate isprovided. The method includes positioning a plurality of masks arrangedin a mask layout over a substrate that is positioned, wherein thesubstrate is positioned in a first plane and the plurality of masks arepositioned in a second plane, the plurality of masks in the mask layouthave edges that each extend parallel to the first plane and parallel orperpendicular to an alignment feature on the substrate, the substrateincludes a plurality of areas configured to be patterned by energydirected through the masks arranged in the mask layout, the plurality ofareas configured to be patterned are spaced apart from each other by oneor more areas not configured to be patterned by the energy directedthrough the masks, and each area of the plurality of areas configured tobe patterned is spaced apart from a closest area of the plurality ofareas configured to be patterned by a shortest distance along adirection offset by at least 5 degrees from directions in the firstplane that extend parallel or perpendicular to the alignment feature onthe substrate. The method further includes directing energy towards theplurality of areas through the plurality of masks arranged in the masklayout over the substrate to form a plurality of gratings in each of theplurality of areas, wherein a number of the formed plurality of gratingsextending along directions in the first plane that are within ±2.5degrees of being parallel or perpendicular to the alignment feature aregreater than a number of the formed plurality of gratings extendingalong directions in the first plane that do not align within ±2.5degrees of being parallel or perpendicular to the alignment feature.

BRIEF DESCRIPTION OF THE DRAWINGS

So that the manner in which the above recited features of the presentdisclosure can be understood in detail, a more particular description ofthe disclosure, briefly summarized above, may be had by reference toembodiments, some of which are illustrated in the appended drawings. Itis to be noted, however, that the appended drawings illustrate onlytypical embodiments of this disclosure and are therefore not to beconsidered limiting of its scope, for the disclosure may admit to otherequally effective embodiments.

FIG. 1A is a top view of three masks arranged over a substrate,according to a conventional patterning process.

FIG. 1B shows an enlarged view of output patterned area of the outputcoupling region from FIG. 1A.

FIG. 2A is a top view of four masks arranged over a substrate, accordingto one embodiment.

FIG. 2B shows an enlarged view of the output patterned area of theoutput coupling region of the substrate from FIG. 2A.

FIG. 3 is a process flow diagram of a method for forming the patternedfeatures of the respective patterned areas shown in FIG. 2A, accordingto one embodiment.

To facilitate understanding, identical reference numerals have beenused, where possible, to designate identical elements that are common tothe figures. It is contemplated that elements disclosed in oneembodiment may be beneficially utilized on other embodiments withoutspecific recitation. The drawings referred to here should not beunderstood as being drawn to scale unless specifically noted. Also, thedrawings are often simplified and details or components omitted forclarity of presentation and explanation. The drawings and discussionserve to explain principles discussed below, where like designationsdenote like elements.

DETAILED DESCRIPTION

Embodiments of the present disclosure generally relate to methods offorming patterns in substrates, for example using masks to transferpatterns to substrates. Although the following is described in referenceto improving methods for forming a waveguide combiner, the improvementsfrom these methods are also applicable to numerous other methods whichuse masks or reticles to create patterns including but not limited tolithography, such as optical lithography or ultraviolet lithography(e.g., extreme UV lithography) as well as lithography using otherportions of the electromagnetic spectrum, such as infrared or X-ray.

FIG. 1A is a top view of three masks 151-153 arranged over a substrate100, according to a conventional patterning process. The substrate 100includes a waveguide combiner 101. The waveguide combiner 101 can beused in an augmented reality device (not shown). The waveguide combiner101 includes an input coupling region 110, an intermediate couplingregion 120, and an output coupling region 130. The intermediate couplingregion 120 can also be referred to as an exit pupil expansion region.Although not shown, in some embodiments, the functions of theintermediate coupling region 120 and the output coupling region 130 canbe designed and located in a same region. The coupling regions 110, 120,130 are used to couple light through the waveguide combiner 101, so thatimages can be displayed to the user of the augmented reality device. Thecoupling regions 110, 120, 130 include pattern features to couple lightthrough the waveguide combiner 101. The patterned features include butare not limited to pillars (e.g., circular pillars and elongatedpillars) and gratings (e.g., line/space gratings). These patternedfeatures can be oriented at a variety of angles relative to a referenceline in the plane of the substrate on which the patterned features areto be formed. For example, if a substrate is considered to be positionedin an XY plane with a thickness of the substrate extending in theZ-direction, the patterned features can be oriented along any angle from0 degrees to 90 degrees relative to a reference line in the XY plane.Furthermore, some embodiments may include multiple patterned featuresoriented along angles different from each other with no particularrelationship determining the difference between these angles. The sizeof the patterned features can also vary. In some embodiments, the sizeof the patterned features can vary according to the critical dimensionof the device being formed, for example from about 10 nm to about 5 um.The gratings include slanted features arranged in patterns across thecoupling regions 110, 120, 130.

The input coupling region 110 is configured to receive incoming lightand transmit light to the intermediate coupling region 120. The inputcoupling region 110 includes an input patterned area 112 including afirst plurality of patterned features 114. In some embodiments, theplurality of patterned features 114 can include a plurality of gratings.The plurality of patterned features 114 can be arranged across the inputpatterned area 112 to extend in a direction defined by an input couplingregion angle 114A. In some embodiments, the input coupling region 110can include additional patterned features (not shown) outside of theinput patterned area 112. These additional patterned features can bealigned along one or more angles that are different from the inputcoupling region angle 114A.

The intermediate coupling region 120 is configured to receive light fromthe input coupling region 110 and transmit light to the output couplingregion 130. The intermediate coupling region 120 includes anintermediate patterned area 122 including a plurality of patternedfeatures 124. In some embodiments, the plurality of patterned features124 can include a plurality of gratings. The plurality of patternedfeatures 124 can be arranged across the intermediate patterned area 122to extend in a direction defined by an intermediate coupling regionangle 124A. In some embodiments, the intermediate coupling region 120can include additional patterned features (not shown) outside of theintermediate patterned area 122. These additional patterned features canbe aligned along one or more angles that are different from theintermediate coupling region angle 124A.

The output coupling region 130 is configured to receive light from theintermediate coupling region 120 and output images from the outputcoupling region 130. The output coupling region 130 includes an outputpatterned area 132 including a plurality of patterned features 134. Insome embodiments, the plurality of patterned features 134 can include aplurality of gratings. The plurality of patterned features 134 can bearranged across the output patterned area 132 to extend in a directiondefined by an output coupling region angle 134A. In some embodiments,the output coupling region 130 can include additional patterned features(not shown) outside of the output patterned area 132. These additionalpatterned features can be aligned along one or more angles that aredifferent from the output coupling region angle 134A.

Three masks 151-153 can be positioned over the waveguide combiner 101. Afirst mask 151 can be positioned over the input coupling region 110 anda first portion 120 ₁ of the intermediate coupling region 120. A secondmask 152 can be positioned over a second portion 120 ₂ of theintermediate coupling region 120. A third mask 153 can be positionedover the output coupling region 130.

The waveguide combiner 101 is positioned in a first orientation relativeto a notch 105 in the substrate 100. The notch 105 in the substrate 100can be used to position the substrate 100 in a first position in whichthe notch is aligned with the Y-axis. In the first orientation, theinput coupling region 110 is spaced apart from the intermediate couplingregion 120 in the Y-direction. Furthermore, the output coupling region130 is spaced apart from the intermediate coupling region 120 in theX-direction in the first orientation. In some embodiments, the X and Yaxis can correspond to axes on equipment used to form the patternedfeatures on the waveguide combiner, such as lithography equipment. Thepatterns in the masks 151-153 are formed to correspond to the patternedfeatures 114, 124, 134 on the respective coupling regions 110, 120, 130when the masks 151-153 are positioned over the coupling regions 110,120, 130 when the substrate 100 is in the first position. Furthermore,the masks 151-153 can also include patterns to form the additionalpatterned features (not shown) mentioned above that can be located inthe coupling regions 110, 120, 130.

FIG. 1B shows an enlarged view of output patterned area 132 of theoutput coupling region 130 from FIG. 1A. FIG. 1B further shows exemplaryelectron beam exposure shots 153M that can be used to fabricate thepatterns in the third mask 153 that correspond to the patterned features134 in the output patterned area 132. The patterned features 134 arealigned along the output coupling region angle 134A. The output couplingregion angle 134A is about 37 degrees relative to the Y-axis (i.e., thedirection in which the notch 105 points). Equipment used to fabricatemasks can operate efficiently along standard angles (e.g., 0 degrees,±45 degrees, and 90 degrees) as well as relatively standard angles(e.g., ±30 degrees and ±60 degrees). For example, equipment used tofabricate masks can generally use a lower number of larger electron beamexposure shots to form patterns in masks within about ±2.5 degrees ofthese standard angles and relatively standard angles. Conversely, thissame equipment cannot produce patterns in masks with the same efficiencyalong non-standard angles (i.e., angles at least ±2.5 degrees offsetfrom the standard and relatively standard angles mentioned above). Thus,a higher number of smaller electron beam exposure shots are needed togenerate patterns along these non-standard angles.

Because the patterned features 134 are aligned along a non-standardangle of 37 degrees, a higher number of smaller electron beam exposureshots are needed to achieve an acceptable pattern in the third mask 153that can then be used to form the patterned features 134 within designspecifications (e.g., acceptable line edge roughness of the patternedfeatures 134). When an attempt is made to use a lower number of largerelectron beam exposure shots to form patterns in masks alongnon-standard angles (e.g., 37 degrees), a staircase effect occurs in thenewly fabricated mask. This staircase effect in the newly fabricatedmask then leads to a corresponding staircase effect in the patterns onthe devices formed with the newly fabricated mask. Thus, the highernumber of smaller electron beam shots are needed to fabricate the maskswith patterns aligned along the non-standard angles, such as 37 degrees.This higher number of smaller electron beam shots can significantlylower throughput for fabricating masks resulting in increased costs.Thus, a solution is needed to avoid the problems associated with formingpatterns in masks along the non-standard angles mentioned above.

FIG. 2A is a top view of four masks 251-254 arranged over a substrate200, according to one embodiment. The substrate 200 includes thewaveguide combiner 101 described above in reference to FIG. 1A. Thesubstrate 200 is similar to the substrate 100 (FIG. 1A) except that thewaveguide combiner 101 is positioned in a second orientation relative tothe notch 105 when compared to the first orientation of the waveguidecombiner 101 relative to the notch 105 as shown in FIG. 1A. In thissecond orientation, the patterned features 114, 124, 134 of the couplingregions 110, 120, 130 are substantially aligned with the X-axis. Usedherein, substantially aligned with an axis or angle refers to a featurebeing aligned within about ±2.5 degrees of the axis or angle.

Positioning the waveguide combiner 101 on the substrate 200 in thissecond orientation causes the patterned areas 112, 122, 132 to be spacedapart from each other in directions that are substantially offset fromthe X-axis or the Y-axis. Used herein, a direction that is substantiallyoffset from an axis refers to a direction that extends at angle at least5 degrees offset from that axis. For example, on the substrate 200, theinput patterned area 112 of the input coupling region 110 is spacedapart from intermediate patterned area 122 of the intermediate couplingregion 120 by a portion of an unpatterned area 107 in a first directionD1 in the XY plane that is at least 5 degrees offset from the X-axis andat least 5 degrees offset from the Y-axis. The first direction D1 canthe direction along which there is a shortest distance between the inputcoupling region 110 and the intermediate coupling region 120. Similarly,the intermediate patterned area 122 of the intermediate coupling device120 is spaced apart from the output patterned area 132 of the outputcoupling region 130 by another portion of the unpatterned area 107 in asecond direction D2 in the XY plane that is at least 5 degrees offsetfrom the X-axis and at least 5 degrees offset from the Y-axis. Thesecond direction D2 can be the direction along which there is a shortestdistance between the intermediate coupling region 120 and the outputcoupling region 130. In some embodiments, the first direction D1 can beperpendicular to the second direction D2.

The four masks 251-254 can be positioned over the waveguide combiner 101of the substrate 200. A first mask 251 can be positioned over the inputcoupling region 110 and a first portion 120 ₁ of the intermediatecoupling region 120. A second mask 252 can be positioned over a secondportion 120 ₂ of the intermediate coupling region 120. A third mask 253can be positioned over a third portion 120 ₃ of the intermediatecoupling region 120 and a first portion 130 ₁ of the output couplingregion 130. A fourth mask 254 can be positioned over a second portion130 ₂ of the output coupling region 130. In some embodiments, each mask251-254 can include an edge aligned with the Y-axis (e.g., edge 252_(E1)) and an edge aligned with the X-axis (e.g., edge 252 _(E2)).Furthermore, in some embodiments, each edge of one or more of the masks251-254, such as all of the masks 251-254, is aligned with the eitherthe Y-axis or the X-axis.

FIG. 2B shows an enlarged view of the output patterned area 132 of theoutput coupling region 130 of the substrate 200 from FIG. 2A. FIG. 2Bfurther shows exemplary electron beam exposure shots 253M that can beused to fabricate the patterns in the third mask 253 that correspond tothe patterned features 134. The patterned features 134 are substantiallyaligned with the X-axis. When patterned features are substantiallyaligned along standard angles (e.g., 0 degrees, ±45 degrees, and 90degrees) and relatively standard angles (e.g., ±30 degrees and ±60degrees) a lower number of larger electron beam exposure shots can beused to form patterns in masks. For example, exemplary electron beamexposure shots 253M of FIG. 2B aligned along the standard angle of 90degrees relative to Y-axis and the direction in which the notch 105points. Thus, the electron beam shots 253M of FIG. 2B are substantiallylarger than the exemplary electron beam exposure shots 153M of FIG. 1B,which are aligned along the non-standard angle of 37 degrees. Moreover,the substantially larger electron beam shots 253M allow substantiallyless electron beam shots to be used to form the patterns in the mask 253relative to the patterns in the mask 153, which can result insignificant reductions in cost. This cost reduction allowed by formingpatterns in masks along standard and relatively standard angles can be acost reduction by a factor of 10 or more compared to forming patterns inmasks along non-standard angles (e.g., 37 degrees).

Because the cost reduction of forming patterns in masks along standardand relatively standard angles is so high (e.g., a factor of ten),significant cost savings can still be achieved even when more masks areused. For example, even though FIG. 2A shows a layout of four masks251-254 being used and FIG. 1A shows a layout of three masks 151-153being used, the layout of the four masks 251-254 still results in asignificant cost savings relative to the layout of the three masks 153because the masks 151-153 shown in FIG. 1A can each cost significantlymore (ten times as much) than the masks 251-254 shown in FIG. 2A.

FIG. 3 is a process flow diagram of a method 1000 for forming thepatterned features 114, 124, 134 of the respective patterned areas 112,122, 132 shown in FIG. 2A, according to one embodiment. The method 1000is described in reference to FIGS. 1A, 1B, 2A, 2B, and 3 .

The method 1000 begins at block 1002, by analyzing an initial layout ofa plurality of components to be formed on a substrate relative to analignment feature on the substrate (e.g., notch 105). Each of theplurality of components in the layout can include a plurality ofpatterned features with each of the plurality of components being spacedapart from each other by one or more unpatterned areas 107 as describedabove.

For example, referring to FIG. 1A, the orientation of the patternedfeatures 114, 124, 134 (plurality of patterned features) of the couplingregions 110, 120, 130 (plurality of components) can be analyzed todetermine the angle at which these patterned features 114, 124, 134extend in the XY plane relative to the direction in which the notch 105points in the XY plane. Furthermore, the coupling regions 110, 120, 130(plurality of components) are spaced apart from each other by one ormore unpatterned areas 107. The coupling regions 110, 120, 130 are alsospaced apart from each other along directions D1, D2 (see FIG. 2A) inthe XY plane which are parallel (Y-direction) and perpendicular(X-direction) to the direction in which the notch 105 points(Y-direction) in the XY plane.

The analysis can determine whether more patterned features in thecoupling regions 110, 120, 130 (plurality of components) align in the XYplane within about ±2.5 degrees of one or more standard angles (e.g., 0degrees, ±45 degrees, and 90 degrees) and/or one or more relativelystandard angles (e.g., ±30 degrees and ±60 degrees) relative to adirection in which the notch 105 points in the XY plane. For example,referring to FIG. 1A, the layout of the coupling regions 110, 120, 130can be analyzed to determine that the patterned features 114, 124, 134are oriented at about 37 degrees in the XY plane relative to thedirection in which the notch 105 points in the XY plane, which is notwithin ±2.5 degrees of the one or more standard angles or relativelystandard angles.

If the analysis at block 1002 determines that a number of patternedfeatures in the coupling regions 110, 120, 130 (plurality of components)that align in the XY plane within about ±2.5 degrees of one or morestandard angles (e.g., 0 degrees, ±45 degrees, and 90 degrees) and/orone or more relatively standard angles (e.g., ±30 degrees and ±60degrees) in the XY plane relative to a direction in which the notch 105points in the XY plane are greater than the number of patterned featureswhich do not align according to those limits, then the method 1000 canend. On the other hand, as in the case shown in FIG. 1A, if the analysisat block 1002 determines that a number of patterned features in thecoupling regions 110, 120, 130 (plurality of components) that do notalign in the XY plane within about ±2.5 degrees of one or more standardangles (e.g., 0 degrees, ±45 degrees, and 90 degrees) and/or one or morerelatively standard angles (e.g., ±30 degrees and ±60 degrees) in the XYplane relative to a direction in which the notch 105 points in the XYplane are greater than the number of patterned features which do alignaccording to those limits, then the method 1000 continues at block 1004.

At block 1004, the layout of the coupling regions 110, 120, 130(plurality of components) is rotated relative to the notch 105, so thatmore patterned features in the coupling regions 110, 120, 130 (pluralityof components) align within about ±2.5 degrees of one or more standardangles (e.g., 0 degrees, ±45 degrees, and 90 degrees) and/or one or morerelatively standard angles (e.g., ±30 degrees and ±60 degrees) relativeto a direction in which the notch 105 points compared to a number ofpatterned features that do not align according to those limits. Forexample, FIG. 2A provides on example of how the layout of the couplingregions 110, 120, 130 (plurality of components) is rotated relative tothe notch 105 and the layout of FIG. 1A. This rotation causes morepatterned features in the coupling regions 110, 120, 130 (plurality ofcomponents) to align within about ±2.5 degrees of the standard anglesand relatively standard angles (described above) relative to thedirection in which the notch 105 points when compared to a number ofpatterned features which do not align according to those limits.

The rotation at block 1004 causes each coupling region 110, 120, 130 tospaced apart from a closest coupling region 110, 120, 130 by a shortestdistance along a direction in the XY plane that is substantially offset(i.e., offset by 5 degrees or more) from directions parallel orperpendicular to the direction in which the notch 105 points in the XYplane. For example, as shown in FIG. 2A, the coupling regions 110, 120are spaced apart from each other by a shortest distance along thedirection D1 in the XY plane, which is substantially offset fromdirections parallel or perpendicular to the direction in which the notch105 points (Y-direction) in the XY plane. Similarly, the couplingregions 120, 130 are spaced apart from each other by a shortest distancealong the direction D2 in the XY plane, which is substantially offsetfrom directions parallel or perpendicular to the direction in which thenotch 105 points (Y-direction) in the XY plane.

At block 1006, a mask layout including a plurality of masks isdetermined for the component layout of the coupling regions 110, 120,130 relative to the notch 105 determined at block 1004. The mask layoutcan be determined for rectangular masks having edges that extendparallel and perpendicular to the direction in which the notch points.For example, FIG. 2A shows a layout of rectangular masks 251-254 to bedisposed over the component layout of the coupling regions 110, 120, 130relative to the notch determined at block 1004. Furthermore, FIG. 2Bshows that the edges (e.g., edges 252 _(E1), 252 _(E2)) of therectangular masks 251-254 extend parallel and perpendicular to thedirection in which the notch 105 points. Although, the individual masks251-254 are rectangular, the overall shape of the mask layout can be anon-rectangular shape, such as an L-shape or a T-shape. In someembodiments, such as the embodiment shown in FIG. 2B, the overall shapeof the mask layout can be an irregular shape.

At block 1008, referring to FIG. 2A, the masks 251-254 are positioned inthe mask layout determined at block 1006 over the substrate 200positioned. The substrate 200 can be described as being positioned in afirst XY plane while the masks 251-254 can be described as beingpositioned in a second XY plane. The first XY plane can be parallel tothe second XY plane. The masks 251-254 can each have edges (e.g., edges252 _(E1), 252 _(E2)) that extend in the second XY plane parallel orperpendicular to the alignment feature (i.e., the notch 105) on thesubstrate 200.

At block 1010, referring to FIG. 2A, energy (e.g., visible light or UVenergy) is directed through the masks 251-254 positioned in the masklayout over the substrate 200 as described at block 1008 to form theplurality of patterned features including the plurality of patternedfeatures 114, 124, 134 in the patterned regions 110, 120, 130. At block1010, a number of the formed plurality of patterned features extendingalong directions in the first XY plane that are within ±2.5 degrees ofbeing parallel, perpendicular, ±30 degrees, ±45 degrees, or ±60 degreesrelative to the alignment feature (e.g., notch 105) are greater than anumber of the formed plurality of patterned features extending alongdirections in the first plane that do not align within ±2.5 degrees ofbeing parallel, perpendicular, ±30 degrees, ±45 degrees, or ±60 degreesrelative to the alignment feature. For example, FIG. 2A shows theplurality of patterned features 114, 124, 134 extend perpendicular tothe direction in which the notch points. Furthermore, although thecoupling regions 110, 120, 130 can include other patterned features (notshown) extending in other directions, the number of the plurality ofpatterned features 114, 124, 134 outnumber these other features.

Overall, while at first glance the mask layout shown in FIG. 2A appearssomewhat staggered and random compared to the mask layout shown in FIG.1A, the mask layout in FIG. 2A and related process described in method1000 can significantly reduce the costs associated with producingpatterned features on a substrate, such as forming gratings for awaveguide combiner. Furthermore, even though FIG. 2A shows four masksbeing used compared to only three masks being used in FIG. 1A, the costof each mask shown in FIG. 2A can be significantly less, such as tentimes less, than the cost of each mask shown in FIG. 1A, so that theoverall cost of the four masks for FIG. 2A is significantly less thanthe cost of the masks shown in FIG. 1A. This reduction in capital costsfor the embodiment shown in FIG. 2A ultimately reduces the costs ofdevices, such as waveguide combiners, generated through the use thesemasks.

While the foregoing is directed to embodiments of the presentdisclosure, other and further embodiments of the disclosure may bedevised without departing from the basic scope thereof, and the scopethereof is determined by the claims that follow.

1. A method of forming patterned features on a substrate comprising:positioning a plurality of masks over a substrate based on a masklayout, wherein the substrate is positioned in a first plane and theplurality of masks are positioned in a second plane when the pluralityof masks are positioned according to the mask layout, the plurality ofmasks in the mask layout have edges that each extend parallel to thefirst plane, each mask having a first edge, the substrate includes aplurality of areas configured to be patterned by energy directed throughthe plurality of masks arranged in the mask layout, the plurality ofareas configured to be patterned are spaced apart from each other by oneor more areas not configured to be patterned by the energy directedthrough the plurality of masks, and each area of the plurality of areasconfigured to be patterned is spaced apart from a closest area of theplurality of areas configured to be patterned by a shortest distancealong a direction offset by at least 5 degrees from directions in thefirst plane that extend parallel or perpendicular to the first edge ofeach mask of the plurality of masks in the second plane; and directingenergy towards the plurality of areas through the plurality of maskswhen the plurality of masks are positioned over the substrate accordingto the mask layout, the directed energy forming a plurality of patternedfeatures in each of the plurality of areas, wherein a number of theformed plurality of patterned features extending along directions in thefirst plane that are within ±2.5 degrees of being parallel orperpendicular to the first edge of each mask of the plurality of masksin the second plane are greater than a number of the formed plurality ofpatterned features extending along directions in the first plane that donot align within ±2.5 degrees of being parallel or perpendicular to thefirst edge of each mask of the plurality of masks in the second plane .2. The method of claim 1, wherein the energy directed through the masksincludes one or more of visible light or ultraviolet energy.
 3. Themethod of claim 1, wherein two or more masks of the plurality of masksare simultaneously positioned over the substrate according to the masklayout.
 4. The method of claim 1, wherein the plurality of masksincludes three or more masks.
 5. The method of claim 1, wherein eachmask has a rectangular shape.
 6. The method of claim 5, wherein anoverall shaped formed by the plurality of masks in the mask layout isnon-rectangular.
 7. The method of claim 5, wherein an overall shapedformed by the plurality of masks in the mask layout is an irregularshape.
 8. A method of forming patterned features on a substratecomprising: positioning a plurality of masks over a substrate based on amask layout, wherein the substrate is positioned in a first plane andthe plurality of masks are positioned in a second plane when the masksare positioned according to the mask layout, the plurality of masks inthe mask layout have edges that each extend parallel to the first plane,each mask having a first edge, the substrate includes a plurality ofareas configured to be patterned by energy directed through the masksarranged in the mask layout, the plurality of areas configured to bepatterned are spaced apart from each other by one or more areas notconfigured to be patterned by the energy directed through the masks, andeach area of the plurality of areas configured to be patterned is spacedapart from a closest area of the plurality of areas configured to bepatterned by a shortest distance along a direction offset by at least 5degrees from directions in the first plane that extend parallel,perpendicular, ±30 degrees, ±45 degrees, or ±60 degrees relative to thefirst edge of each mask of the plurality of masks in the second plane;and directing energy towards the plurality of areas through theplurality of masks when the masks are positioned over the substrateaccording to the mask layout, the directed energy forming a plurality ofpatterned features in each of the plurality of areas, wherein a numberof the formed plurality of patterned features extending along directionsin the first plane that are within ±2.5 degrees of being parallel,perpendicular, ±30 degrees, ±45 degrees, or ±60 degrees relative to thefirst edge of each mask of the plurality of masks in the second planeare greater than a number of the formed plurality of patterned featuresextending along directions in the first plane that do not align within±2.5 degrees of being parallel, perpendicular, ±30 degrees, ±45 degrees,or ±60 degrees relative to the first edge of each mask of the pluralityof masks in the second plane.
 9. The method of claim 8, wherein theenergy directed through the masks includes one or more of visible lightor ultraviolet energy.
 10. The method of claim 8, wherein two or more ofthe masks of the plurality of masks are simultaneously positioned overthe substrate according to the mask layout.
 11. The method of claim 8,wherein the plurality of masks includes three or more masks.
 12. Themethod of claim 8, wherein each mask has a rectangular shape.
 13. Themethod of claim 12, wherein an overall shaped formed by the plurality ofmasks in the mask layout is non-rectangular.
 14. The method of claim 12,wherein an overall shaped formed by the plurality of masks in the masklayout is an irregular shape.
 15. A method of forming gratings on asubstrate comprising: positioning a plurality of masks over a substratebased on a mask layout, wherein the substrate is positioned in a firstplane and the plurality of masks are positioned in a second plane whenthe masks are positioned according to the mask layout, the plurality ofmasks in the mask layout have edges that each extend parallel to thefirst plane, each mask having a first edge, the substrate includes aplurality of areas configured to be patterned by energy directed throughthe masks arranged in the mask layout, the plurality of areas configuredto be patterned are spaced apart from each other by one or more areasnot configured to be patterned by the energy directed through the masks,and each area of the plurality of areas configured to be patterned isspaced apart from a closest area of the plurality of areas configured tobe patterned by a shortest distance along a direction offset by at least5 degrees from directions in the first plane that extend parallel orperpendicular to the first edge of each mask of the plurality of masksin the second plane; and directing energy towards the plurality of areasthrough the plurality of masks when the masks are positioned over thesubstrate according to the mask layout, the directed energy forming aplurality of gratings in each of the plurality of areas, wherein anumber of the formed plurality of gratings extending along directions inthe first plane that are within ±2.5 degrees of being parallel orperpendicular to the first edge of each mask of the plurality of masksin the second plane are greater than a number of the formed plurality ofgratings extending along directions in the first plane that do not alignwithin ±2.5 degrees of being parallel or perpendicular to the first edgeof each mask of the plurality of masks in the second plane.
 16. Themethod of claim 15, wherein the plurality of areas includes an inputcoupling region, an intermediate coupling region, and an output couplingregion.
 17. The method of claim 16, wherein the intermediate couplingregion is a closest area to the input coupling region, and a shortestdistance between the intermediate coupling region and the input couplingregion extends along a first direction.
 18. The method of claim 17,wherein the intermediate coupling region is a closest area to the outputcoupling region, and a shortest distance between the intermediatecoupling region and the input coupling region extends along a seconddirection.
 19. The method of claim 18, wherein the first direction isperpendicular to the second direction.
 20. The method of claim 15,wherein two or more of the masks of the plurality of masks aresimultaneously positioned over the substrate according to the masklayout.